Hey there, Nigel.
Not having a stock QCX-30, I can't speak to its performance on other bands.
But, as for my stock QCX-17, I have enjoyed more QSOs with it on 30m than on any other band...would love to QSO ZS6RN on 30m !
I was informed yesterday by Alan, G1FXB of the 6-band QCX rig by Andreas, DM5MU, found near the bottom of the page at:
https://www.qrp-labs.com/qcx/qcxgallery.html 
Very interesting rig !
72 / 73,
Bill, N4QA